Question

13)) An auto driver moving with a speed of 36 km/h sees a child standing in the middle of the road. He applies break and brings his vehicle to rest in 5 seconds just in time to save the child. If the total mass of the auto and the driver be 450 kg then calculate the force of brakes. 3

Answer 1

Given

Mass of the vehicle along with driver m = 450 kg

Initial velocity u = 36 km/hr = 36×(5/18) = 10 m/s

Final velocity v = 0 m/s (as the vehicle stops)

And the time taken to stop the vehicle t = 5 seconds.

Now we know acceleration a = (v - u)/ t

a = (0 - 10)/5 = -2 m/s ( - sign indicates that the vehicle is experiencing deaceleration)

Also we know Force F = mass × acceleration

F = 450 × (-2 )

F = -900 N ( - sign indicates that the force is applied in a direction opposite to that the motion of the vehicle)